Working memory refers to the retention of information in conscious awareness when this information is not present in the environment, to its manipulation, and to its use in guiding behavior. Understanding the cognitive and neural bases of working memory functions is central to understanding normal cognition, as well as its neurological and psychiatric dysfunctions. The research proposed here investigates the neural mechanisms supporting working memory within the framework that working memory is accomplished through the coordinated recruitment, via attention, of brain systems that have evolved to accomplish sensory-, representation-, and action-related functions. This framework can be summarized as depicting working memory as the temporary activation of long-term memory (LTM) representations. The aims of this application target direct empirical tests of the activated LTM model that will not be subject to the limitations that characterize this literature to date. Specifically, they will allow direct testing of whether brain activity elicited by the engagement of LTM reappears (within the same brain regions, and with the same quantitative pattern) during working memory storage. To better understand the neural bases of working memory storage - and its ramifications on normal and abnormal brain functioning - it is crucial to explore the nature of this activated LTM mechanism. Each proposed experiment will feature the analysis of fMRI neuroimaging experiments with a novel multivariate analysis technique - multi-voxel pattern classification. This research addresses a stated area of high importance for the NIMH, with computational models being used in conjunction with neuroimagaing data to elucidate the neural circuitry supporting the retention of information in the brain. Impairments of working memory are seen in many neurological (e.g., Alzheimer's disease, Parkinson's disease, traumatic brain injury), psychiatric (e.g., schizophrenia, depression, dissociative disorders), and developmental (e.g., attention deficit disorder, dyslexia, specific language impairment) disorders. And in normal human cognition, individual differences in working memory have been linked to the effects of manipulating dopamine on high-level cognitive tasks, to performance in grade school, to reading ability, and to fundamental cognitive abilities such as language comprehension, problem solving, LTM, and general fluid intelligence. Achieving a better understanding of the neurobiological organization of working memory functions, therefore, may have important implications for the clinical treatment and cognitive rehabilitation of patients with brain-related disorders.